1. Field of the Invention
This invention pertains to the construction of the box member of tubular goods and more specifically to the installation of a resilient ring such as a seal ring or a corrosion barrier ring within the accommodating groove of such a member.
2. Description of the Prior Art
Tubular goods used in the oil and gas industry are subjected to highly corrosive environmental and working conditions, especially such elements as CO.sub.2 and H.sub.2 S. In addition, the products are subjected to axial load, vibrations, torque, bend and turbulence of flowing liquids and gases, often carrying erosion and corrosion producing suspended particulates. A susceptible corrosion location within a tubular string, if unprotected, will corrode and result in failure of the wall at that point. Such failure is not only inconvenient, it can be disruptively costly and even dangerous.
It is common to coat the internal diameter of tubular products. Such coating minimizes corrosion throughout the length of the pipe string. However, such coating does not form a resilient bond. Hence, when the coating is scarred, which might be caused by tightening the connection, there is created a corrosive-susceptible area.
Corrosion barrier rings have, therefore, been employed in pipe connections to provide certain advantages which cannot be obtained by coating alone. A corrosion barrier ring is located typically adjacent to a shoulder in the box end (or to a shoulder in the box-type threads of a suitable auxiliary coupling member) where the nose of the pin end abuts when the connection is made up. Such ring is typically made of a Teflon PTFE material or a fiber-filled Teflon material that cold flows on contact to form a corrosion barrier with respect to the adjacent box or box-type threads and the pin threads. Teflon is a trademark of E. I. DuPont de Nemours, Inc. for polytetrafluoroethylene (PTFE).
Tubular connecting ends can be made to be either tapered or non-tapered; however, the preference in the industry is for tapered ends. With tubular products having threads of conventional configuration where the threads are uniformly dimensioned with respect to pitch, the threads of coupled parts are screwed together until a stop shoulder is encountered or until there is a reduction in thread depth, which can also be referred to as a stop. Then, depending on how much torque is applied, the connection is made up. For example, for standard grooves with a width dimension of 0.130 inch, with normal machine tolerances applicable to drill pipe, the location of pin-end-nose to box-end-shoulder can be reliably located within .+-.0.020 inches. A suitable recess concentric with the internal annulus at the rear of the box-type threads provides a space for a corrosion barrier ring. The location of such space is very predictable since the location of the stop just described, is closely controlled.
The placement of the corrosion barrier rings into their accommodating grooves, particularly on a production basis, has heretofore been time consuming and an expensive hand-manipulation step. To manipulate such rings is dexterously difficult and can cause injury to the fingers of the persons who do the installing. Such rings are deformable, but have poor plastic memories. Therefore, if a radial deformation is made in the ring to make it small enough to pass through the thread area to the vicinity of the groove, it must be physically forced outwardly into conformity with the groove. Working with the threads and sometimes spreading fingers over the edge or rim of the box member is potentially injurious and painful to the fingers and the webbing between the fingers. Moreover, there is no certainty that the ring is well seated in the groove, which is vital to accomplish its corrosion barrier purpose. About the only way heretofore to test if the ring is in place is to make up the joint by screwing a pin end in place. This, again, is time consuming and there is still no certainty or way of checking that the ring is properly seated in its groove since these parts are hidden from view when the connection is made up. In addition, corrosion barrier rings are not normally reusable. They permanently deform to accommodate to a particular connection configuration. A test makeup could damage or distort the ring for a subsequent in-use makeup. If damaged, then the removal of the ring is yet another time-consuming step.
Therefore, it is a feature of the present invention to provide an improved method of installing a corrosion barrier ring into the box member of a pipe without requiring hand manipulation and which assures that the ring is neither distorted nor improperly seated.
It is another feature of the present invention to provide an improved tool or apparatus for manipulating a corrosion barrier ring so as to ensure its proper seating in the accommodating groove behind the threaded area of a tubular box member end.